Technical Field
The present invention relates to a method of manufacturing a pneumatic tire, a shaping device and a pneumatic tire.
Related Art
Conventionally, in manufacturing a radial tire, a green case is formed by winding tire component members which include at least one layer of a carcass ply in a cylindrical shape. Next, the green case is adhered to a tread ring arranged on an outer peripheral side of the green case by expanding the green case into a toroidal shape radially outward with the supply of a fluid into the green case thus shaping a green tire. Then, the green tire is subjected to vulcanization molding within a mold die thus shaping the green tire into a product tire.
In the carcass ply, carcass cords are arranged approximately uniformly. However, there has been a case where the array of the carcass cords is disturbed at the time of shaping so that irregularities in cord openings between the carcass cords become increased. When the irregularities in cord openings between the carcass cords are increased, unevenness on a tire surface of the product tire is increased thus giving rise to a defective appearance or lowering of uniformity of the tire.
On the other hand, in a method of manufacturing a cross ply tire disclosed in JP 2012-131168 A, prior to setting of a green case into a vulcanizing mold die, pre-shaping of the green case is performed by expanding the green case with a fluid supplied to the inside of the green case, and the green case is held in an inflated state where a largest outer diameter of a tread portion becomes 60% to 90% of a largest inner diameter of a tread forming surface of the vulcanizing mold die for a predetermined time. This manufacturing method aims at the suppression of the disturbance in the array of the carcass cords and the enhancement of uniformity of the tire through the suppression by making the green tire easily be formed along a surface of a mold die and by changing a shape of the tire in a stepwise manner from the green case to a product tire through a green tire.